It was also actually pretty fun!

  • tomkatt@lemmy.worldEnglish
    13314·
    5 months ago

    Give me more of this and less of the politics. This is what I come to Lemmy for.

    • cm0002@lemmy.worldOP
      88·
      5 months ago

      Not really, I pulled it together from a bunch of random posts lol

      Maybe I should write one, but in essence you:

      • Stop all non-OS essential services

      • Create a filesystem in a chunk of RAM

      • Pull essential OS files from the installed OS into it recreating needed directories (Though you could probably just use a tiny pre-built distro but meh)

      • Pivot root into it

      • Reload services (when they restart they’ll be restarted in the context of where you pivot rooted, prior they’re still running under the context of the installed OS)

      • Unmount the boot drive

      • Then do what ever you need to do

      • ???

      • Profit

  • aMockTie@lemmy.world
    28·
    5 months ago

    What happens if the SSH session closes before dd finishes? Sounds pretty badass but I don’t think I would trust this approach in prod lol

    • cm0002@lemmy.worldOP
      32·
      5 months ago

      Well the 1 SSH session bit was for dramatic meme-effect lol, you can actually connect back without issue (at least it did for me) so worst case if you weren’t working in tmux you’d just have to start dd again

      Worst worst case, you’d just end up back where you were probably heading before anyways, KVM/IPMI

      • aMockTie@lemmy.world
        6·
        5 months ago

        Sure, I suppose as long as sshd is up and running in the ramdisk environment (which you mentioned in another comment, along with all other services) you could always reconnect. Very neat and clever!

      • aMockTie@lemmy.world
        11·
        5 months ago

        True, but I was more thinking about the issue of reconnecting in general when you just nuked sshd.

    • InnerScientist@lemmy.world
      2·
      5 months ago

      As long as you only copy off the disk, you can just reboot and the whole system in RAM vanishes and the normal system boots again for the second try.

    • cm0002@lemmy.worldOP
      36·
      5 months ago

      I had a server I rented from a provider in a data center and I wanted to image (dd) the drive for archival before I decommissioned it from my infrastructure.

      Normally, you can’t really do that with the OS running and you would have to shut down and insert a live USB or something and temporarily boot from that. The server being a faraway rental the only option was to open a ticket so that they could enable an out-of-band management option like KVM or IPMI. Which would allow you to control a machine as if you had a physical monitor, keyboard and mouse in front of you. With that you can attach flash drives, shutdown, restart, see the POST/BIOS/UEFI screens etc remotely .

      But, I didn’t want to wait 6-8 hours for them to enable that so instead I put together a process that would “boot” me into another distro “installed” into a RAM disk (kinda like how live CD/USB works) from the currently installed and running OS without rebooting

      From there I could unmount the boot disk and do what ever I wanted from there, I could have even wiped the disk entirely and installed a entirely different distro if I wanted

      • AVincentInSpace@pawb.socialEnglish
        10·
        5 months ago

        How do you do that? What minimal distro did you use? Did you make it yourself? How reliable is pivot-root? How many tries did it take you to do that successfully?

    • Croquette@sh.itjust.works
      17·
      5 months ago

      RAM is still memory, so you can put anything in there, like an OS.

      With pivot_root, you can change where the root is. So you pivot into your OS in RAM, which becomes the root of the system.

      At that point, you can do pretty much anything you would normally do with your OS, like unmount a HDD.

      I’ve never personally done it, but that’s a simplified explanation of what OP did.

  • Pacmanlives@lemmy.world
    151·
    5 months ago

    Hopefully you don’t lose power or something else bad happens or there goes your data

    • Ajen@sh.itjust.works
      5·
      5 months ago

      If that happens, they just fall back to the first option of waiting for their provider to set up the IPMI.

  • bss03@infosec.pub
    13·
    5 months ago

    I’ve never gotten pivot_root to work well / as documented. Major props for being able to pull this off. Hopefully you didn’t have much time where a connection-drop would require a reboot. SSH in the new root on an alternate port before the pivot? idk.

    • cm0002@lemmy.worldOP
      8·
      5 months ago

      Really? It seemed to go pretty smooth for me, SSH dropped once I think when I reloaded the services (expected), but after that I was able to connect back fine on the same port no issue

      • bss03@infosec.pub
        1·
        5 months ago

        It’s been a LONG time since I tried, but ISTR it complaining that it couldn’t move the old_root because it was in use? But, when I’d fuser it, the only think that was using it was my shell (using it as the current directory).

    • cm0002@lemmy.worldOP
      5·
      5 months ago

      Damn lol wish I would have come out sooner lmao Seems a tad more complicated though, I don’t remember having to compile anything at least

  • ChojinDSL@discuss.tchncs.de
    7·
    5 months ago

    Check out dattobd sometime. It’s a tool that allows you to make a snapshot of a block device for backups, while the OS is running. Useful if your filesystem doesn’t support snapshots.

  • Prison Mike@links.hackliberty.org
    6·
    5 months ago

    I’ve been killing myself in my free time to get a NanoPi R6S to boot from an SD card; wish I had this expertise.

    Edit: I didn’t say this very clearly, I’ve been killing myself to build and compile U-Boot, the Linux kernel then building an image to write to an SD card that’ll actually boot.

    • cm0002@lemmy.worldOP
      7·
      5 months ago

      Heh, this expertise is built on hundreds of “Why tf won’t X boot from Y!!” and solid research skills lol you’ll get there

      • Prison Mike@links.hackliberty.org
        1·
        5 months ago

        Oops, I realize now that my comment made it seem like I can’t figure out how to write an image to external media and boot it properly. It was actually more intense than that, so I’ve updated it.

    • PlexSheep@infosec.pub
      2·
      5 months ago

      Not sure about your hardware, but try to look up if it requires a special kernel, like the RPi 5 (which only runs on raspbian because they ship that kernel)

      • Prison Mike@links.hackliberty.org
        1·
        5 months ago

        The manufacturer ships several tools but a lot of the necessary files are shared from Google Drive, and each time I try to download one it says “download limit exceeded.” My goal is to build something more vanilla — I can see that the hardware is supported in the mainline kernel so I’m doing this with tons of trial and error (which I don’t mind).

        I’m doing everything in a Dockerfile so once I’m there the goal is to clean it up and push it to GitHub.

  • Nine@lemmy.worldEnglish
    4·
    5 months ago

    Once I figured out how to netboot the os into memory that’s how I run all my nodes :)

  • smb@lemmy.mlEnglish
    3·
    5 months ago

    i had experimented with kexec and takeover.sh to install a distro that was not available by my provider.

    it resulted in some scripts i now (triggered by this thread) have published (in a nonready state):

    http://github.com/tobinq/goaround

    the scripts may be in bad shape but i successfully changed one preinstalled ubuntu to a devuan with what is in these scripts. however i didn’t work on them for month now and am not sure about that last state… so its experimental only.